@article{StaigerSeufertArandetal.2019,
  author    = {Staiger, Simona and Seufert, Pascal and Arand, Katja and Burghardt, Markus and Popp, Christian and Riederer, Markus},
  title     = {The permeation barrier of plant cuticles: uptake of active ingredients is limited by very long-chain aliphatic rather than cyclic wax compounds},
  series = {Pest Management Science},
  volume    = {75},
  journal   = {Pest Management Science},
  number    = {12},
  doi       = {10.1002/ps.5589},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-204778},
  pages     = {3405-3412},
  year      = {2019},
  abstract  = {BACKGROUND: The barrier to diffusion of organic solutes across the plant cuticle is composed of waxes consisting of very long-chain aliphatic (VLCA) and, to varying degrees, cyclic compounds like pentacyclic triterpenoids. The roles of both fractions in controlling cuticular penetration by organic solutes, e.g. the active ingredients (AI) of pesticides, are unknown to date. We studied thepermeabilityof isolated leaf cuticularmembranes from Garcinia xanthochymus andPrunus laurocerasus for lipophilic azoxystrobin and theobromine as model compounds for hydrophilic AIs. RESULTS: The wax of P. laurocerasus consists of VLCA (12\%) and cyclic compounds (88\%), whereas VLCAs make up 97\% of the wax of G. xanthochymus.We showthat treating isolated cuticles with methanol almost quantitatively releases the cyclic fraction while leaving the VLCA fraction essentially intact. All VLCAs were subsequently removed using chloroform. In both species, the permeance of the two model compounds did not change significantly after methanol treatment, whereas chloroform extraction had a large effect on organic solute permeability. CONCLUSION: The VLCA wax fractionmakes up the permeability barrier for organic solutes, whereas cyclic compounds even in high amounts have a negligible role. This is of significance when optimizing the foliar uptake of pesticides.},
  language  = {en}
}
@phdthesis{Popp2005,
  author    = {Popp, Christian},
  title     = {Cuticular transport of hydrophilic molecules with special focus on primary metabolites and active ingredients},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-15174},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2005},
  abstract  = {The plant cuticle as an interface between the plant interior and the adjoining atmosphere plays an important role in any interaction between the plant and its environment. Transport processes across the cuticles were the object of countless research since many decades. However, bulk of the work done was focused on transport of lipophilic molecules. It is highly plausible to examine the penetration of lipophilic compounds, since the cuticle is dominated by lipophilic compartments itself, and the most crop protection agents have lipophilic character. As a result of this research, cuticular transport of lipophilic compounds is relatively well understood. Since several years, examinations were expanded on transport of hydrophilic molecules. In the present study, a direct comparison was made between transport properties of lipophilic and hydrophilic compounds, which allows an objective assessment of the mechanism governing their penetration. The results of this present study debunked the existence of two different pathways across isolated cuticles of Hedera helix (English ivy), a lipophilic and a hydrophilic pathway. This finding was supported by examinations regarding to accelerator and temperature effects on the mobility of both pathways, because the hydrophilic path is insensitive to them - in contrary to the lipophilic one. The lipophilic pathway is rigorously restricted to lipophilic molecules and the hydrophilic pathway is only accessible for hydrophilic molecules. Uncharged hydrophilic compounds can cross the cuticle even the molecules are of relatively large dimensions. In contrast to that, dissociable compounds with a molar volume higher than 110 cm³ mol-1 are excluded from cuticular penetration. Differences in the mobility of uncharged and dissociable molecules might be a hint towards the chemical nature of the polar pathways. It is assumed, that both, cellulose and pectin fibrils, traverse the cuticle which are originated from the epidermal cell wall. While uncharged carbohydrates might be able to penetrate across a pathway made up of cellulose and pectin, dissociated amino acids might be restricted to the cellulose path. This could be a plausible explanation for the higher mobility and the higher cuticle/water partition coefficients of the carbohydrates compared with the amino acids. A hydrophilic pathway was found with isolated grapevine cuticles, too. The apparent size selectivity of the hydrophilic pathway implies transport via narrow pores. From the present data, a mean pore radius of 0.31 nm (H. helix) or rather 0.34 nm (V. vinifera) was calculated. The absolute number of pores per cm² is 1.1 x 109 for H. helix and 3.3 x 109 for V. vinifera cuticles. This finding and the enlarged pore size distribution of grapevine cuticles might be an explanation for the transport of uncharged and dissociable hydrophilic compounds of higher molar volume like paraquat dichloride - in contrast to ivy membranes Wax extraction of ivy membranes uncovers additional pores, which explains the increased mobilities of the hydrophilic compounds across dewaxed membranes. From these extensive measurements it is very conspicuous, that the bulk of cuticular water transpiration occurs via the polar pathway. Since the work was focused on cuticular penetration of primary metabolites like amino acids and carbohydrates, a mechanistic explanation of leaching processes is obtained, simultaneously. In cuticular research, an inconsistent terminology regarding the transport path of the hydrophilic compounds was used. The term 'hydrophilic pathway' is definitely correct, since it makes no statement with regard to the shape of this path. In contrast to that, the terms 'polar pore' or 'aqueous pore' could imply that there is a tube or rather a water-filled tube traversing the cuticle. However - at this point of time - the imagination about the shape of this path is a pathway across interfibrilar gaps within polysaccharide strains. The proposed diameter of these interfibrilar gaps fits very well to the diameter determined in this study. Therefore, the imagination of a pore is not unfounded, but it is a very narrow pore, definitely. Additionally, this pathway is a very straight pathway which corresponds to this simplified imagination. An expanded study was done with paraquat dichloride, which was applied as aqueous droplets on grapevine cuticles. It is assumed that these model membranes reflect transport properties which are very close to that of relevant crops and weeds. The predominating parameter for paraquat penetration is the moisture, either originated from a relative humidity of at least 75\% or provided by added chemicals. There is a tendency for good suitability of hygroscopic additives. Increased paraquat penetration was also obtained by raised concentrations and removal of the cuticular waxes.},
  subject      = {Kutikula},
  language  = {en}
}
@phdthesis{Popp2004,
  author    = {Popp, Christian},
  title     = {Identifizierung von Aminos{\"a}uren als Teile der Substratbindungstasche des Kationentransporters 1 der Ratte (rOCT1) und Interaktion des rOCT2 mit der schwachen Base Chinin},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-12349},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2004},
  abstract  = {Zusammenfassungen 83 5 Zusammenfassungen 5.1 Zusammenfassung Durch Expressionsklonierung wurde 1994 der erste organische Kationentransporter, rOCT1, aus der Ratte isoliert (Gr{\"u}ndemann et al., 1994). 1999 wurde eine Aminos{\"a}ure in der 11. Transmembrandom{\"a}ne von rOCT1 entdeckt, welche Teil der Substratbindungstasche dieses Transporters war (Gorboulev et al., 1999). Zielsetzung der vorliegenden Arbeit war es weitere funktionell relevante Aminos{\"a}uren zu identifizieren. Ein Vergleich der „Helical Wheels" aller 12 hypothetischen Transmembrandom{\"a}nen zeigte eine Akkumulation von 5 OCT und OCTN spezifischen Aminos{\"a}uren in der vierten Transmembrandom{\"a}ne auf einer Seite. Bei diesen Aminos{\"a}uren handelte es sich um K215, W218, Y222, T226 und V229. Es wurden verschiedene Punktmutationen an diesen Positionen eingef{\"u}hrt. Es zeigte sich mit Hilfe radioaktiv markierter Substrate von rOCT1, dass selbst Substitutionen durch strukturell verwandte Aminos{\"a}uren bei den flankieren Aminos{\"a}uren zu einem Ausfall des rOCT1 vermittelten Substrattransport f{\"u}hrte. Weiterhin schien an Position 218 f{\"u}r den rOCT1- vermittelten Transport von TEA eine aromatische Aminos{\"a}ure von großer funktioneller Relevanz zu sein. Wir vermuten hier eine Kationen p-Elektronen Interaktion des aromatischen Ringsystems des Tryptophans mit der positiven Ladung des TEA. Versuche mit den Mutanten des Tyrosins 222 zeigten ebenfalls {\"A}nderungen bei den Transportraten und Affinit{\"a}ten verschiedener Substrate. Eine Kationen-p Interaktion konnte ausgeschlossen werden, jedoch war die Affinit{\"a}t der Mutante Y222F zum TPeA um einen Faktor 20 gegen{\"u}ber dem Wildtyp erh{\"o}ht. Weiterf{\"u}hrende Untersuchungen mit der Zwei- Elektrodenspannungsklemme zeigten unterschiedliche Affinit{\"a}ten des TPeA zum Wildtyp im Vergleich zum mutierten Protein in seiner nach außen bzw. nach innen gerichteten Konformation. War die Form der Inhibierung des TEA-induzierten Stromes durch TPeA beim Wildtyp kompetitiv, so zeigte sie bei der Mutante einen nicht-kompetitiven Charakter. Die Mutante T226A zeigte ebenfalls {\"A}nderungen in Affinit{\"a}t und Selektivit{\"a}t. Bei allen transportierenden Mutanten zeigte sich, dass der Transport von MPP nicht oder kaum ver{\"a}ndert war, hingegen wurden sehr starke {\"A}nderungen der Transportcharakteristika von TEA gefunden, was auf verschiedene Substratbindungsstellen in rOCT1 hinweist. Diese Versuche zeigen deutlich die funktionelle Relevanz und die Beteiligung der mutierten Aminos{\"a}urepositionen an der Substratbindetasche von rOCT1. In Versuchen, in welchen Chinin als Inhibitor des rOCT2 vermittelten Transports genutzt wurde, passierte Chinin mittels Diffusion in seiner ungeladenen Form die Oozytenmembran und hemmte rOCT2 von der Innenseite. Dies k{\"o}nnte der Grund f{\"u}r die nicht-kompetitive Form der Inhibition der TEA-Aufnahme durch Chinin sein. Diese Versuche wurden dadurch best{\"a}tigt, dass die protonierte Form des Chinins eine kompetitive Form der Inhibition zeigte und den Transporter von außen hemmte.},
  subject      = {Ratte},
  language  = {de}
}